Electrochemical Fabrication of Copper-Based Hybrid Microstructures and Mechanism of Formation of Related Hierarchical Structures on Polypyrrole Films

The surface electrochemistry of polypyrrole–polystyrene sulfonate (PPy–PSS) thin films is exploited for the fabrication of novel hybrid copper-based microstructures. The electrochemical deposition of the copper-based materials at the PPy–PSS film is strongly dependent on the electrode potential. This dependence is studied at three different potentials: 0.10, 0.00, and −0.10 V vs SCE. Hierarchical micro/nanostructures made of copper hydroxysulfate salts are only formed at 0.10 V vs SCE and are replaced with branched and single microcrystals of Cu2O covered by a thin layer of Cu(OH)2 at 0.00 and −0.10 V vs SCE, respectively. The different structures can be coupled on the same film through a simple fabrication procedure to give hybrid microstructures. These novel hybrids consist of a central microcrystal (deposited at −0.10 V vs SCE) and a surrounding contour of welded nanosheets (deposited at 0.10 V vs SCE). The mechanism of nucleation and growth of the hierarchical micro/nanostructures formed at 0.10 V vs SCE is also reported. These structures are made from the assembly of nanoparticles into nanowires, nanosheets, and microclusters. These microclusters have a flowerlike shape within which each nanosheet forms a petal of the flower. The nucleation of the clusters is shown to be progressive.